Ask Tom why: Do tornadoes travel southwest to northeast?

July 30, 2011

Dear Tom,

Do tornadoes travel southwest to northeast?

—Tony Palumbo, Tinley Park

Dear Tony,

Tornadoes move in the same direction and with the same speed as the thunderstorms that are producing them (though in the dissipating stage, some tornadoes stretch into "rope funnels" that lag behind their attachment to the parent thunderstorms by many hundreds of feet). Most thunderstorms move from the southwest and, consequently, so do most tornadoes. Tornado researcher Dr. Tetsuya Fujita (1920-1998) cataloged 17,081 tornadoes whose movement was known and found that tornadoes move from all directions: from the southwest, 59 percent; from the west, 19 percent; from the northwest, 11 percent; south, 6 percent; southeast, 2 percent; and 1 percent each from the north, northeast and east. The killer Plainfield tornado (29 deaths) of Aug. 28, 1990, moved from the northwest.